Previously, AB block copolymers have been developed which show good action as dispersants, which use aromatic carboxylic acids incorporated in the A segment to provide binding to a pigment surface. Such copolymers are described, for example, in Hutchins et al., U.S. Pat. No. 4,656,226, issued Apr. 7, 1987. Hutchins et al. note that many carboxylic acids, when incorporated onto the A segment of the block copolymer, can provide improved dispersant characteristics. Preferred acids which can be so used include benzoic acid, 2-,3-,4-nitrobenzoic acid, 3,5-dinitrobenzoic acid, 1-naphthoic acid, and 3-chlorobenzoic acid.
While the Hutchins et al. compositions provide excellent dispersant characteristics, many of these compounds exhibit color changes upon extended exposure to light and aging. Because dispersants are often used in mixtures designed to produce a specific color, changes in the color cover time are undesirable.